1. Field of the Invention
The present invention relates to a tilt lock device for an outboard boat motor.
2. Description of the Related Art
The prior art shows a tilt lock device for an outboard motor in Japanese Patent Application Publication No. 2-58155 (TILT LOCK DEVICE FOR OUTBOARD MOTOR).
This prior art reduces a tilt-up operation force by a simple structure in addition to a basic function of the tilt lock device. As shown in FIGS. 1, 4, and 5 of this publication, this device comprises a cylinder 8, a piston 12 movably inserted in the cylinder 8, a piston rod 11 mounted to the piston 12, first and second oil chambers 8a and 8b defined in opposite sides of the piston 12, passages 13 and 14 provided in the piston 12 for interconnecting these first and second chambers 8a and 8b, check valves 15 (first relief valves) and 16 provided in intermediate portions of the passages 13 and 14, a communication passage 24 for interconnecting these first and second chambers 8a and 8b outside the cylinder 8 so as to bypass the piston 12, a switch valve 37 provided in an intermediate portion of the communication passage 24, a second relief valve provided in the switch valve 37, and comprising a valve seat 42, a valve body 44 and a spring 47.
The first and second relief valves are for buffering the shock that an outboard motor B receives when the outboard motor B collides against an obstacle such as driftwood or a log.
In the above-described prior art, however, since the check valve 16 is connected to the piston 12, the first relief valve 15 also connected to the piston 12 experiences a restriction in size because a space for mounting the first relief valve 15 is small and therefore, there is the disadvantage of difficulty to sufficiently exhibit a buffering performance of the tilt lock device.
Further, since the second relief valve having the same function as that of the first relief valve 15 is provided as a separate member from the first relief valve 15, the tile lock device occupies a large space. Furthermore, the communication passage 24 is extended outwardly from the cylinder 8, and the switch valve 37 is provided in the intermediate portion of the communication passage 24, there is a disadvantage in that a pipe laying operation at the time of assembling is troublesome.